Never understood the concept of "preferred" seating on AC anyway. Except for the slight benefit of being able to get off the aircraft a tad bit faster, they are no different. In fact, as mentioned earlier, in some aircraft, they have less pitch. Agents give them away at the airport, and if I'm in the back, I always look to seats further forward when I check in online or at a kiosk, and they are usually available, so I assume these "elite" seats are released at check in. CO does the same thing, for example, the first 8 - 9 rows on an RJ145 are held for elites until check in, when anyone can select them.

On the other hand, at least with RJ's and smaller, they usually have to have more people in the front, especially when they are not so full, as the baggage goes in the back, and they need to weight balence with pax. Maybe someone with more technical expertise can talk about this in more detail, not sure about with the Embraer's, but I know this is the case for CR7s and smaller. Have been moved to E+, and even first on UA several times when I was a general member when loads were light, and they needed additional weight in the front.